The present invention relates to an airbag system for protecting the body of an occupant in a seat when a vehicle is subjected to a lateral impact force.
In airbag systems for vehicles that are practically used these days, an airbag is contained folded in a center pad of a steering wheel or a instrument panel of the vehicle on the passenger-seat side. According to the airbag systems of this type, the body of an occupant in the vehicle is caught on the airbag that is inflated in an instant by gas when the vehicle undergoes a head-on collision. The airbag serves to absorb the forward force of inertia that acts on the occupant and prevents the occupant from suffering a second collision with the steering wheel, instrument panel, etc.
Also, there have been developed side airbag systems in which an airbag is contained folded in a seat or a side face of a cabin of a vehicle, e.g., the inside of a door. When the vehicle undergoes a side impact, the airbag of one such side airbag system is inflated in an instant by gas, thereby preventing an occupant in the vehicle from suffering a secondary collision with the inside of the door or the like.
When the vehicle is subjected to a lateral impact force, an inside wall of the vehicle body moves toward the center of the cabin or the side opposite to the impact side. Also, a seat cushion, along with a side sill and the floor, moves toward the center of the cabin. Since the body of the occupant seated on the seat cushion is not fixed to the cushion, however, it is induced to stay where it is by the force of inertia. As the inside wall of the vehicle body, moving toward the center of the cabin, approaches the occupant, therefore, they may possibly undergo a secondary collision with each other. The side airbag system serves to maintain the safety of the occupant's body in case of such a side impact of the vehicle.
FIGS. 8, 9 and 10 show a conventional seat-mounted side airbag system. This airbag system is attached to a passenger seat that includes a seat cushion 1 and a seat back 2. A space section 4 surrounded by a pad member 3 is formed in a flank portion of the seat back 2 on the door side. The space section 4 contains therein an airbag module 7, which includes an inflator 5, an airbag 6, etc. The pad member 3 of the seat back 2 is covered by a covering 8. A front covering 8a and a side covering 8b of the covering 8 are stitched together at a corner stitch portion 8c of the pad member 3. Thus, the pad member 3 is concealed under the covering 8 including this stitch portion 8c.
The airbag system described above is provided with a sensor (not shown) for detecting the force of a side impact on a vehicle. When the sensor detects a lateral impact force on the vehicle, it gives an operational command to the inflator 5. Thereupon, the inflator 5 is actuated so that an inflating gas such as nitrogen gas therefrom is introduced in an instant into the airbag 6. This inflating gas causes the airbag 6 to break the stitch portion 8c and inflate, as indicated by two-dot chain line in FIG. 8.
As shown in FIGS. 9 and 10, a lower half 6a of the airbag 6 bulges out between a trunk 10a of an occupant 10 and an inside wall 6c of the vehicle body. An upper half 6b of the airbag 6 inflates between a head 10b of the occupant 10 and the inside wall 6c of the vehicle body. Thus, the upper half (trunk 10a and head 10b) of the body of the occupant 10 can be prevented from undergoing a second collision with the inside wall 6c. Airbag systems constructed in this manner are described in Jpn. Pat. Appln. KOKAI Publication Nos. 6-227348, 8-67228, etc., for example.
As described above, the conventional seat-mounted side airbag system has the space section 4 in the door-side flank portion of the seat back 2, and the inflator 5 and the airbag 6 are housed in the space section 4. Also, the space section 4 contains a regulating member 5' for restricting the inflating direction of the airbag 6. Further, the pad member 3 is concealed by stitching the front and side coverings 8a and 8b together at its corner stitch portion 8c.
The seat back 2 is stuffed with the pad member 3 in order to improve the comfortableness of the seat for the occupant. To attain this, the airbag 6 must be contained folded compactly in a limited space inside the seat back 2. This narrow space is also expected to contain the inflator 5 and the regulating member 5' for restricting the inflating direction of the airbag 6, as well as the airbag.
Thus, the airbag system arranged in this manner entails use of a large number of components, complicated construction, and a lot of assembling processes, resulting in an increase in cost. In order to protect a wide area of the occupant's body ranging from the trunk 10a to the head 10b by means of the single airbag 6, moreover, the airbag must be securely bulged toward a space between the body of the occupant 10 in the seat and the inside wall 6c of the vehicle body. Accordingly, the shape of the airbag 6 is complicated, and it is difficult to inflate the airbag into an optimum shape by introducing the gas in an instant into all parts of the airbag.